The present invention relates to a strawberry-dyeing agent and a dyeing solution for use in preparing strawberry dyed which have widely been used as, for instance, additives for confectionery such as cakes and jellies as well as a method for dyeing strawberries with the dyeing solution.
Strawberries have poor storability as compared with other fruits, ripen fast after harvesting and the shelf-life at ordinary temperature is only 2 days. Moreover, natural dyestuffs of the strawberry are thermally unstable and severely lose the color. When storing the strawberry having such a short shelf-life after harvesting, cooler-storage has usually been adopted. For instance, there has been adopted a method comprising the steps of mixing strawberries with liquid sugar or solid sugar, immediately cooling the mixture down to -30.degree. C. or lower and then storing it at a temperature of not more than -20.degree. C.
However, the color fading already discussed above also proceeds in the cooler-stored strawberry, the appearance thereof becomes substantially inferior to that for those just harvested and further the texture and the shape retention become brittle and poor, respectively.
In addition, there has been a method for dyeing a variety of fruits with dyes to prevent the color fading of the dyestuffs thereof. For instance, Lecture II "Manufacture of Canned Foods", pp. 291-294, issued on September first, Showa 44 (1969), by Canners Association of Japan discloses a method for preparing cherries preserved in syrup which comprises dyeing cherries by immersing them in a dyeing solution comprising an artificial dye and an organic acid for adjusting pH thereof to 4.5 contained in a tub or tank, rapidly cooling them, then sufficiently washing with water, canning them together with syrup, degassing the contents of the can, i.e., the cherries and the syrup, sealing the can and sterilizing the contents of the sealed can.
However, such a dyeing method requires the use of a multistage immersion process and a water washing process and, thus the practice of this method is quite troublesome. Moreover, if fruits having a high air content are treated by this method, oxidation and browning of the fruits are accelerated during the storage. Further, it would take several days for dyeing the fruits if a natural dye is substituted for an artificial dye.